The combination of lower, more aerodynamic vehicle hood lines and increased heat rejection from diesel engines due to improved emission control devices results in ever increasing difficulty in cooling system design. One tactic is to increase the maximum allowable coolant temperature in the engine to increase the heat transfer capability of a given size radiator. However, excessive coolant temperature can result in engine component failure due to boiling. Current engines use electronic controls to measure the coolant temperature and take steps such as turning on the fan or decreasing the power output when the temperature is too high. The goal of these schemes is to keep the coolant under a particular temperature. The common practice today is to use fixed temperature values as set points for this type of control scheme. Fan events and derates for the engine happen at pre-programmed temperatures selected with the goal of keeping the coolant temperature in a pre-selected range.
However, there are several noise factors that can not be accounted for using a single set of temperature values. Coolant pressure is perhaps the biggest noise factor, but there are many other factors that can not be accounted for. For example, if the temperature is high while the pressure is low, there is risk of boiling in the head, EGR cooler or water pump seal cavity. The pressure in the cooling system is regulated by a pressure cap and top tank system and is also a function of altitude.
The cap and top tank are supplied by the vehicle OEM rather than the manufacturer, so there is a large amount of variation in their performance and the same vehicle may operate at many different altitudes. An engine manufacturer is faced with making a trade-off—risking engine damage by selecting temperature set points that are too high, or risking being uncompetitive by setting our temperature limits too low, resulting in OEM dissatisfaction and excessive derates for the end user. Among the considerations that go into the selection of set points is estimating what would happen at the extremes of variation of unknowns such as coolant pressure.
The result is typically a trade off where compromises are made both in engine reliability and in radiator size. Accordingly, what is needed is a system and method for minimizing this trade off. The method and system should be cost effective, easy to implement and adaptable to existing engines. The present invention addresses such a need.